The present invention is related to a mass-flow sensor arranged on a membrane. Fluid flows past this arrangement. In particular, the measuring element exhibits a higher temperature than the medium. The measuring element measures the intensity of the flow of the medium based on the transfer of heat into the medium.
U.S. Pat. No. 4,501,144 discusses a mass-flow sensor in which a measuring element is arranged on a membrane, and a medium flows past the membrane. The measuring element exhibits a higher temperature than the medium, and the intensity of the flow of the medium is measured from the transfer of heat into the medium. In addition, a media-temperature measuring element is mounted on a frame that retains the membrane. The temperature of the measuring element is kept at a constant level in relation to the temperature of the media-temperature measuring element. Furthermore, U.S. Pat. No. 4,501,144 discusses suspending the thin membrane in a frame of monocrystalline silicon.
German Published Patent Application No. 41 06 287 discusses methods for etching recesses into silicon plates having a 100-orientation. These recesses can be used to produce silicon frames, in which a membrane is suspended.
German Unexamined Patent Application No. 40 03 473 describes a method for manufacturing motion sensors, in which a recess is etched into a silicon wafer having 110-orientation. This etching process can also be used to produce a silicon frame in which a membrane is suspended.